Various surgical techniques benefit from the use of non-native flat supporting members inserted into the patient's body to apply pressure to the patient's own tissue. Such implanted supporting members can be made from synthetic material, natural material, whether harvested from the patient or elsewhere, or composites of both synthetic and natural materials. When using harvested natural material, it may be desirable to treat the source tissue to alter its physical properties to insure it is biocompatible and does not cause an adverse reaction with the patient's immune system.
One example of a sheet-like support structure for use in a range of surgical techniques IS described in U.S. Pat. No. 6,197,036. This patent discloses a pelvic floor reconstruction surgical patch made from natural or synthetic biocompatible material. According to the '036 patent, the preferred material for use in the patch is synthetic fabric made from polyester, more preferably, collagen coated polyester. The patch has a number of holes which are arranged in a specific manner with respect to the patch's corners.
Another material that can be used as a patch to reinforce soft tissue is processed porcine intestinal tissue. Examples of support structures made from such material include the Surgisis® Gold™ Hernia Repair Grafts, the Surgisis® Soft Tissue Grafts, and the Surgisis® IHM™ Inguinal Hernia Matrix, all manufactured by Cook Surgical, of Bloomington, Ind. and described in Cook Surgical's literature.
An increasingly widespread technique for treating female urinary incontinence is that of sling suspension. Examples of such procedures and equipment which can be employed are discussed in U.S. Pat. Nos. 5,112,344, 5,899,909, and 6,273,852 B1. In this technique, a flat supporting member is used to treat female urinary incontinence by permanently positioning a strip-like sling beneath the patient's urethra. By implanting the sling and then adjusting the sling to apply a desired level of force to the patient's urethra, the amount of pressure which the patient must thereafter exert to void her bladder is increased, improving continence. The sling member is preferably implanted in the patient's tissue by using a needle to draw the sling into its approximate position. Then, the surgeon can make fine adjustments to properly locate the sling member, and to apply the required amount of tension to the tissue requiring support.
Although originally implanted slings were anchored in the patient's body, for example, by using sutures to join the sling ends to the patient's pelvis, it is now more common to leave the sling ends unattached. The sling is maintained in position through friction between sling material and the patient's own tissue, in particular, in the case of a sling implanted in the lower abdomen, with the rectus fascia. This approach is known as a “self-anchoring” or “tension-free” procedure.
In self-anchoring sling support procedures it is important that the sling be held firmly in place by friction with the patient's tissue. Should the ends of the sling slip, then insufficient support will be provided for the urethra to alleviate incontinence, and the procedure will be unsuccessful. It is also important that the sling material used be strong enough to withstand, without rupture or tear, any forces that are encountered following implantation, for example, when the patient sneezes.
Slings can be made from tape or mesh. Numerous implant materials have been considered and used for sling procedures, including both synthetic mesh and natural tissue.
Although easy to sterilize, strong and inexpensive, synthetic mesh material has a number of shortcomings which will be discussed in further detail below. Just by way of example, when synthetic mesh material is used as a sling support, the roughness of the synthetic mesh may lead to abrasion of the patient's urethra, and that can cause infection and/or erosion of the patient's tissue.
When performing sling support procedures, it is important to use an implant which is well-tolerated by the patient's immune system. To this end, sling supports can be made from processed natural material. One example of such a processed tissue sling support is the Stratasis® TF support, manufactured by Cook Urological, Inc. of Spencer, Ind. The Stratasis® TF support is a three-dimensional extracellular matrix which includes collagen, non-collagenous proteins, and biomolecules that is made of natural biomaterial derived from the small intestine of pigs. The Stratasis® TF support is gradually replaced by the patient's body.
A traditional sling procedure involves placing a narrow strip of an implant material (natural tissue or synthetic mesh) under the urethra and securing it to the rectus fascia or other portions of the patient's anatomy with sutures to hold the implant in position during the healing process.
More recently, a newer technique has been used to place a strip of synthetic mesh under the urethra without securing the mesh in place with sutures. In this technique, the implant member is held in place during the healing process by the friction between the mesh and the surrounding tissue. This improvement, which employs specialized instrumentation, has helped reduce operative time and has made the procedure less invasive.
Although each of these techniques has demonstrated good results, each has a number of potential complications, due, in part, to the type of material from which the sling is formed.
Synthetic mesh is used with the self-anchoring techniques. Among the benefits to using synthetic mesh material is that the friction of the synthetic mesh with the surrounding tissue allows for suture-free placement of the mesh strip. “Kits” are commercially available which include a suitable mesh implant member and the small needles needed to pass the synthetic mesh implant member into the patient's body; few other surgical instruments are required. This has resulted in a simpler and less invasive procedure in which only small incisions are required, no patient tissue need be harvested, and just a short hospital stay is required.
Clinical articles have suggested that the synthetic mesh material used in this procedure is subject to a higher risk of causing erosion of the patient's tissue than are natural materials. Furthermore, the synthetic mesh material has a higher risk of infection than does natural material, probably because the mesh provokes a foreign body reaction from the patient's body or may harbor bacteria around the mesh. The synthetic mesh material also tends to have a greater amount of scar tissue formation around the mesh fibers, instead of vascular ingrowth.
Natural materials, for example, autologous, allograft, or xenograft tissues, or soft collagen fiber engineered materials, which are used in traditional techniques, offer such benefits as a lower risk of erosion than the synthetic materials. Natural materials also have a lower risk of infection, presumably because there is no foreign body reaction. The natural materials also experience better tissue ingrowth than the synthetic materials because they are made up of collagen fibers, which can serve as a tissue-building framework.
Disadvantageously, the natural materials require sutures be used to anchor the material in position. To implant the natural material slings, traditional instrumentation is used. Such instrumentation often requires more invasive surgical techniques, larger incisions, harvesting of the patient's own tissue for use as the sling, and consequently, may result in a longer hospital stay.
Although natural support members offer many benefits when used in the manner described above (for example, they are not abrasive), they also are generally more expensive than their synthetic counterparts, since such support members are derived from natural source materials that must be treated to insure sterility, stability and biocompatibility.
Given the expense of natural support members, it is desirable to reduce the amount of natural material used in each support member without also reducing the self-anchoring properties, positioning ability, strength or durability of that support member.
There also exists a long-felt and unsolved need for a support system, and, in particular, a sling suspension system which offers the respective cost and tolerance benefits of both synthetic and natural materials, without the weaknesses of either of those techniques.
Although some doctors are satisfied with the results that they have achieved using synthetic mesh sling kits, other doctors prefer not to use the synthetic materials due to the materials' higher potential for complications such as the occurrence of infection or foreign body reaction around the mesh, or urethral or vaginal wall erosion due to the mesh. In some cases of erosion, mesh has been observed to unravel, creating a sharp “fishing line” effect, which can slice through the patient's tissue. This is not a concern with natural fibrous materials such as autologous, allograft, or xenograft tissues, which elongate less and do not neck down under load.
Existing surgical hardware, such as the McGuire™ suture guide, which has a central suturing hole, and available from C. R. Bard, Inc. of Murray Hill, N.J., is based upon what is known as the “Stamey” needle. Although such devices could be modified for use in the field of this invention, they do not possess all the requisite properties for the uses envisioned for this invention.
Thus, there exists a long-felt and unsolved need for a sling suspension system which offers the distinct benefits of both synthetic and natural materials, without the weaknesses of either of those techniques.